An example of various hydrogen storage materials proposed by various study groups may include metallic hydrides, chemical hydrides (including NaBH4, KBH4, LiBH4, and the like), metal-organic frameworks (MOF), nano structure materials (GNT, GNF, and the like), polymer-metal complex compounds, etc. However, the storage materials have problems in that: 1) hydrogen storage is less than a reference value (6wt. %) of minimum hydrogen storage proposed so as to practically use the hydrogen storage materials in Department of Energy (DOE) of USA, 2) the repeatability of the hydrogen storage is degraded, 3) hydrogen adsorption and desorption conditions are very stringent, 4) a material structure collapse phenomenon is caused in the hydrogen adsorption and desorption process, and 5) it is difficult to be commercialized due to a need to develop the reproduction process.
However, in the case of the organic-transition metal hydride complexes that are recently filed as patent by Hanwha Chemical R&D Center, it can be easily commercialized than the hydrogen storage materials according to the related art by Kubas binding of hydrogen and unique transition metals Ti, Sc, and V, since 1) a larger amount of hydrogen can be stored at higher efficiency, 2) hydrogen can be adsorbed and desorbed under less stringent conditions, e.g., the conditions that adsorption is performed under 25° C. and 30 atmospheric pressure and desorption is performed under 100° C. and 2 atmospheric pressure, and 3) there is little the structure collapse phenomenon at the time of performing the repetitive hydrogen adsorption and desorption (KR Patent Nos. 10-2007-0090753 and 10-2007-0090755).
The synthesis method of the organic-transition metal hydride disclosed in the above Patents proposes a method that includes hydrodehalogenation reaction (-M-X bond→-M-H bond) and simultaneously uses hydrogen feeding sources and catalysts as the hydrodehalogenation reaction. However, the hydrodehalogenation reaction, which simultaneously uses the hydrogen feeding sources and catalysts, has the following problems.
First, as problems associated with the poisoning phenomenon of the catalyst, Cl− ions produced during the reaction are adsorbed onto surfaces of catalysts to reduce active surface areas of catalysts and HCl produced during the reaction dissolves precious metal components of catalysts to reduce active sites of catalysts.
Second, as problems associated with a use of inorganic hydroxide necessary for the reaction, inorganic hydroxide used as neutralizers, which mitigate the poisoning phenomenon and the dissolution phenomenon, reacts with Cl− and HCl to produce the following reaction.
(for example) Case of using NaOH as inorganic hydroxide
NaOH+Cl−→NaCl+OH−
NaOH+HCl→NaCl+H2O
When organic solvents other than H2O are used, it is difficult to separate NaOH and target compounds from each other. Also, OH− approaches Ti—H bonding of the target compounds to form Ti—OH bonding and H2O approaches Ti—H bonding of a product and converts it into Ti oxide.
Third, as problems associated with separation and purification of products, since products are basically mixed with catalysts, it is difficult to separate them from each other. As a result, it is difficult to be applied to a commercialization process exceeding the scale obtained in the experiment.
Fourth, as problems associated with the used solvents, since 2-alkanols are used as the hydrogen feeding sources and the reaction solvents so as to increase the reaction efficiency, it is most preferable that a high boiling point is required to provide energy necessary for the complete hydrodehalogenation reaction to these 2-alkanols and the solvents including one or more α-H (α-hydrogen) as the hydrogen feeding sources are selected and applied. However, since the 2-alkanols having the above characteristics include an excessive hydrocarbon chain to produce various reaction by-products, there is a problem in that it is difficult to further separate and purify them.
Therefore, the typical hydrodehalogenation reaction using the hydrogen feeding sources and the catalysts has limitations in that it is difficult to stably prepare the organic-transition metal hydride complexes and the yield of products is low due to the above problems.